This invention relates in general to vehicles and, in particular, to the hood for a vehicle engine enclosure.
More specifically, but without restriction to the particular use which is shown and described, this invention relates to a perforated hood with an air scoop for use in vehicles, such as, for example, construction machinery in the form of crawler tractors, scrapers, loaders and the like. The perforated hood with an air scoop of the invention directs ambient air to the vehicle radiator for effective cooling without establishing a heat exchange relationship with the engine.
In conventional cooling systems, such as employed in tractors and the like, external air is circulated through a hood or grill by a fan assembly for delivery to the engine coolant heat exchanger. The flow path established in such systems directs ambient air drawn into the engine compartment into direct thermal contact with the operating vehicle engine thereby elevating the temperature of the ambient air before delivery to the radiator.
The level of the temperature of the air passed through the vehicle tractor is a significant factor in establishing the cooling efficiency of the heat exchanger. The introduction of an air flow above ambient temperature causes a corresponding rise in temperature of the engine coolant in the top tank of the radiator. Such an elevation of the temperature of the coolant in the top tank occurs, because the efficiency of the radiator is dependent on several factors, some of which are the temperature difference between the air flow and coolant, the temperature drop of the coolant through the radiator, and the temperature rise of the air flow caused by thermal contact with the vehicle engine. Based on the foregoing relationship, the heat transferred by the engine to the air flow being directed to the radiator is a parameter, which directly affects the overall efficiency of the vehicle heat exchanger.
Prior art attempts to alleviate the problems associated with the heat rise of the radiator air flow caused by the vehicle engine have been unsatisfactory. Known systems have failed to provide suitable thermal isolation of the engine from the air drawn through the hood area to be effective in attaining increased radiator efficiency. Such techniques have also been deficient in delivering an optimum quantity of air to the heat exchanger for superior cooling. In addition, the employment of air delivery structures in the past to avoid the thermal effect of the engine have hindered servicability of the engine and have failed to incorporate desirable engine sound absorbing and debris protection capabilities.
Certain prior art designs, attempting to avoid the effects of engine temperature on cooling, require complete engine enclosures, which interfere with normal dissipation of the engine heat. Examples of prior art vehicle engine hoods and engine compartment designs are disclosed in U.S. Pat. No. 3,982,600 to Gerresheim, et al., issued Sept. 28, 1976, and U.S. Pat. No. 4,071,009 to Kraina issued Jan. 31, 1978, and U.S. Pat. No. 4,086,976 to Holm, et al., issued May 2, 1978.